Apparatus for forming articles

ABSTRACT

Die segments in a die body are movable between a normally open blank-receiving position and a closed blank-reforming position. In the blank-reforming position, the die segments engage the die body along surfaces which are disposed at an acute angle to the longitudinal axis of the press ram used to move the die segments into their blank-reforming position. The press ram maintains the die segments in the blank-reforming position while a piston punch fluid pressurizes a hollow blank to reform the blank into the shape of a forming cavity defined by the die segments, a die stripper head and a neck die of the ram. The die stripper is coupled to the die segments to eject a reformed article and to accept a hollow blank for reforming. The angle of engagement of the die segments with the die body to the longitudinal axis of the ram is small enough that the amount of force which the ram must exert to keep the die segments together is relatively low. A pump coupled to the press ram is capable of providing additional pressurization of the hollow blank in the event that the piston punch is incapable of displacing sufficient liquid to effect the high-pressure required for reforming.

United States Patent [111 2,

[72] Inventors Forrest H. McMeen FOREIGN PATENTS M i 1,370,852 7/1964 France 4 72 54 William F. Gresham, San Clemente, both v of, Calif. Primary ExammerRlchard J Herbst 2 1 APPL No 770 93 Attorney-Christie, Parker & Hale [22] Filed Oct. 21,1968

[45] Patented July 13, 1971 [7 3] Assignee VSI Corporation Pasadena, Calif.

ABSTRACT: Die segments in a die body are movable between a normally open blank-receiving position and a closed blankreforming position. In the blank-reforming position, the die segments engage the die body along surfaces which are disposed at an acute angle to the longitudinal axis of the press ram used to move the die segments into their blank-reforming [54] APPARATUS FOR FORMING ARTICLES position. The press ram maintains the die segments in the l4 Clalms 6 Drawing Flgs' blank-reforming position while a piston punch fluid pres- U-S- surizes a hollow blank to reform the blank into the shape of a 0 M1321! 26/08 forming cavity defined by the die segments, a die stripper head 0 Search r 58, and a neck of the ram The tripper is coupled to [he 29/42l die segments to eject a reformed article and to accept a hollow blank for reforming. The angle of engagement of the die seg- [56] References Cited ments with the die body to the longitudinal axis of the ram is UNITED STATES PATENTS small enough that the amount of force which the ram must 1,711,445 4/1929 Burvenick 72/58 exert to keep the die segments together is relatively low. A

72/58 pump coupled to the press ram is capable of providing addi 72/58 tional pressurization of the hollow blank in the event that the 72/58 piston punch is incapable of displacing sufficient liquid to ef- 72/ 58 feet the high-pressure required for reforming.

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APPARATUS FOR FORMING ARTICLES The present invention relates to an apparatus for pressure forming of articles, such as hollow blanks, within a die. The apparatus is especially well suited in hydraulically reforming articles having undercuts, or similar irregular configurations, where extremely high pressures are required to effect article reforming.

Hydraulically wrought articles are presently formed by inserting preformed blanks into dies and filling the hollow interiors of the blanks with a liquid such as water or oil. A piston punch of a press ram is advanced into the hollow interior of each blank to pressurize the liquid. The blank is reformed by liquid pressure until it conforms to the configuration of the forming cavity of the die, at which time a reformed article is produced.

In the past, the reforming dies were constructed in at least two pieces to permit the insertion of hollow blanks and to allow the removal of reformed articles from the forming cavity. The die construction was such that a parting line between die pieces was present along a plane at right angles to the direction in which the press ram moved. The parting line coincided with the greatest circumferential dimension of the forming cavity to facilitate blank placement and reformed article removal. The multiple piece forming dies were held together by the press ram during the reforming operation.

The multiple-piece construction of the forming dies, together with the requirement for holding the dies in their forming position by the press ram, resulted in the necessity of using extremely large capacity press rams. Large capacity press rams were necessary because the parting lines of the die pieces or segments were transverse to the direction of press ram movement resulting in extremely high, pressuregenerated forces from the liquid acting against the press ram. As an example of the capacity requirements of the press ram to maintain the forming dies in their forming position, the manufacture of conventional doorknobs has heretofore typi cally required a press ram capacity of from 60 to 100 tons to resist forming pressure of the order of 50,000 p.s.i.

The requirement for extremely large capacity press rams obviously results in increased tooling costs. Moreover, maintenance costs are increased as press ram capacity increases. The relatively high increment of article-forming costs attendant with large capacity press rams results in relatively highpriced articles to the ultimate consumer.

Hydraulically wrought articles produced on a production basis must be produced by a forming apparatus which admits to relatively rapid positioning of the die pieces or segments between their blank-receivingarticle discharge position and their blank-reforming position. This requirement must be met with die segments which are accurately indexed and maintained in their blank reforming position in order to prevent unsightly parting line marks on the reformed articles.

ln addition, because of the configuration of some articles, the piston punch of conventional press ram assemblies is incapable of displacing sufficient liquid to effect article forming. This limitation has, heretofore, limited the use of the efficacious technique of hydraulically forming articles.

The present invention contemplates an apparatus for the pressure forming of articles in a press which materially reduces the force required to hold the die segments together during the pressure forming of articles while accurately and firmly maintaining its die segments in proper position during a pressure forming operation.

In one form, the present invention contemplates an improved die assembly in an apparatus for pressure reforming of hollow blanks into reformed articles. The die assembly includes at least two displaceable die segments disposed within a die body for movement between a spaced-apart, blank-receiving reformed article discharge position and a blank-reforming position. The die segments are engaged with the die body 7 along an acute angle to the line of movement of a press ram as- 'sembly. This acute angle, preferably less than 45, effects a material reduction in the closing force required to be asserted by a press ram assembly on the die segments during the reforming of hollow blanks into reformed articles. The die segments in their blank-reforming position define at least a portion of a forming cavity and a bore. The bore opens into the forming cavity for passage of a piston punch of the press ram assembly. The apparatus may further include means for reciprocating the press ram assembly to and away from the die segments, means for supporting the press ram assembly, and means for moving the die segments from their blank-reforming position to their blank-receiving-reformed article discharge position.

The acute angle of the die segments with the die body effects a transfer of a portion of the forming force through a blank being reformed to the die segments and ultimately into the die body. This portion of the reforming force must not, therefore, be overcome by the press ram assembly. In short, the die closing force required of the press ram must only be sufficient to counteract a relatively small proportion of the total forming force.

ln preferred form the means for moving the die segments from their blank-reforming position to their blank-receivingreformed article discharge position utilizes a sleeve which has an annular flange in engagement with the die segments through an annular recess therein, and means for biasing the sleeve, and hence the die segments, toward the ram assembly. Such means may include, for example, a spring disposed to act on the sleeve and die body to urge the sleeve toward the ram assembly. The flange of the sleeve coordinates the movement of the die segments between their open, article dischargeblank-receiving position and their closed, mating, articlereforming position.

Preferably, a die stripper is included for receiving hollow blanks to be reformed and for discharging reformed articles. The die stripper is capable of transmitting a closing force of the press ram assembly to the coordinating sleeve and then to the die segments. The die stripper has a head which forms a portion of the reforming cavity when the die segments are in their mating position. This head may be coupled to the sleeve through a shaft disposed axially in the sleeve for movement therein. Means such as a spring may act on the head to effect relative movement between the die stripper and the sleeve and effect head displacement toward the press ram assembly in ex cess of that which would be possible if the die stripper and the sleeve were rigidly coupled together. The die stripper, then, is the responsible member for transmitting the closing force through the sleeve to the die segment from a hollow blank being acted upon by the press ram assembly.

Many articles to be hydraulically formed require the use of a neck die on the press ram assembly. Accordingly, for this type of article formation a neck die is included in the press ram assembly which is capable of entering the bore defined by the die segments in their mating position around the neck of a blank to be reformed. The neck die, then, defines a portion of the reforming cavity.

In instances where the article to be reformed has a relatively narrow neck for the entrance of the piston punch, it may be necessary to augment the pressure generated by the piston punch to completely reform the article. An embodiment of the present invention augments the pressure generated by the piston punch through a pressure pump assembly which is operable to pressurize the interior of a hollow blank in the forming cavity. Preferably, this pressure pump includes a piston which is engageable on a stationary portion of the apparatus to compress fluid in communication with the hollow interior of the blank through a bore in the piston punch.

In order to remove reformed articles from the aforementioned neck die, a stripper sleeve may be provided in the press ram assembly. This sleeve is operable as the press ram assembly moves away from the die segments to engage the neck of a reformed article and discharge it from the neck-forming die.

The apparatus of the present invention is particularly valuable in that it provides an efficacious means for hydraulically forming parts having complex configurations. These complex configurations require a high forming pressure for detailed definition. The closing force required to keep the die segments in their mating, blank-reforming position is relatively low because of the acute angle of engagement of the die segments with the die body. The force to which the press ram assembly is subjected, by the pressurized fluid in the hollow blank, can be reduced to a minimum by decreasing the taper or inclination of the die body's walls. That is, the capacity required for the press can be significantly lowered by reducing the angle defined by the inclined walls of the die body and the axial line of movement of the ram. The smaller the angle, the smaller the resulting component of force acting on the ram occurring from the pressure within the forming cavity. Holddown means can also be employed where extremely high pressures are required. Substantial cost savings are therefore obtained, both during initial installation of the press as well as during its operation. Conventional doorknobs, bottlelike containers, articles having undercut surfaces, and a variety of other intricately shaped articles are examples of the types of articles which may readily be formed by the apparatus of the present invention.

By means of the unique die body and segmented die construction of the present invention, even the most complex shaped articles can be readily removed from the die after being formed. This is accomplished by the unique die stripper which is capable of discharging articles from the die segments as the die segments open after the reciprocating press ram is disengaged therefrom. Moreover, the die stripper acts as a carrier of hollow blanks to be reformed and, in its position away from the reforming position, is conveniently situated for the placement of such hollow blanks. Coordinated movement of the die segments is effected by the coupling member to assure accurate placement and maintenance of the segments in their mating position. Articles having narrow necks are readily formed by the augmenting pressurization of the pressure pump assembly. Formed articles are readily removed from the neck die by the stripper sleeve.

These and other features, aspects and advantages of the present invention will become more evident from the following description, appended claims and drawings, in which:

FIG. 1 is an elevational, schematic view of a hydraulic form ing apparatus of this invention, including holddown means;

FIG. 2 is a fragmentary elevational view of the holddown mechanism of FIG. 1 when in clamping position;

FIG. 3 is a fragmentary elevational view, partly in half section, of the apparatus shown in FIG. 1, the press of the apparatus being shown just prior to commencement of the forming operation;

FIG. 4 is a fragmentary side elevational view, partly in half section, of the press of FIG. 2 during the forming operation, the elevational view being at 90 of FIG. 3;

FIG. 5 is a fragmentary plan view of the press shown in FIG. 3, taken along line 55 of FIG. 3; and

FIG. 6 is a fragmentary plan view of the press of FIG. 4, taken along line 6-6 of FIG. 4!.

FIGS. 1 and 2 illustrate a generalized version of the hydraulic forming apparatus of the present invention. Except for the holddown assembly illustrated in these two Figures, the apparatus is identical to that shown in the balance of the Figures. As such, identical reference numerals refer to identical parts.

In general, FIGS. 1 and 2 illustrate a hydraulic forming apparatus 10 which includes a press bolster 12, a die assembly 14, a press ram assembly 16 and a holddown assembly 18.

Die assembly l4 includes a plurality of movable die segments 20. These movable die segments are disposed for movement in response to actuation by the-press ram assembly along a path at an acute angle to the line of movement of a press ram 22 of the press ram assembly. This angled path is determined by the angle of engagement of the movable die segments with their confining die body 24. As will become more apparent as this description proceeds, the angle of the movable die segments in engagement with their supporting die body 24 determines the amount of force or capacity of the press ram assembly which is required to properly seat the movable die segments in their reforming position against the unseating or displacement force of the pressurizing fluid. In general, however, as the angle of engagement approaches the line of movement of the press ram, smaller and smaller press ram assembly capacities are required. That is, as the angle between the engaged surfaces of the movable die segments and the die body to the longitudinal axis of the press ram approaches zero, the required capacity of the press ram assembly approaches a minimum.

Die assembly 14 includes a die stripper 26. Die stripper 26 is biased towards press ram assembly 16 by a spring within the die assembly. Die body 24 includes means for movable die segments 20 to accurately track along the aforementioned angled path between a preformed blank-receivingreformed article discharge position and a reformed article forming position. These tracking means will be described with reference to FIGS. 3 through 6.

Press ram assembly 16 includes a neck die assembly 28, a piston punch 30 and a drive assembly 32. Neck die assembly 28 has a die portion 34 in the form of an annular flange which is responsible for forming a portion of the reformed article, as will be more apparent with the description of FIGS. 3 through 6. Piston punch 30 is disposed for entrance into the neck of a preformed blank 36 for pressurizing hydraulic fluid therein and expanding the preformed blank by the force of the pressurized hydraulic fluid into the configuration of the movable die segments, the top of the die stripper and neck die portion 34. Neck die assembly 28 is carried by a neck die holder 38 which is secured to press ram 22 by compression springs 40.

The press ram assembly is capable of movement toward and away from die assembly M through drive assembly 32. Drive assembly 32 includes drive sleeves 42 which are engaged for translation, in a standard manner, with upright tubes 44. A conventional punch press motor 4l6 is drive coupled with the press ram assembly through lines 48 in a conventional manner. Crossover bar 50, secured to sleeves 412, carries press ram 22.

Holddown assembly 18 may be used to further augment the capacity reduction of the press ram assembly afforded by the angled engagement of movable die segments 20 with die body 24.

The holddown means includes clamp members 52 which have engaging shoulders 54 disposed for engagement with bosses 56 on neck die holder 38. Clamps 52 are spring biased into an open position out of engagement with bosses 56 through springs 58. Clamps 52 are pivotally mounted through pins 60 to clevises 62. Clevises 62 are mounted on die body 24. Actuating fingers 64 are carried by shafts 66. Shafts 66 are in turn mounted for translation in crossover bar 50.

Compression springs 68 engage the crossover bar and actuating fingers 64. Thus, the translation facility of shafts 66 allows the balance of the press ram assembly to move slightly further in the direction of die assembly 114 after fingers 64 are arrested by engagement with clamp members 52. Lateral support members 70, secured to sleeves 42, prevent fingers 64 from moving laterally away from press ram 22 when the fingers engage clamp members 52.

The operation of the generalized embodiment of the invention illustrated in FIGS. l and 2 will now be described. Initially, a preformed blank 36 is placed on die stripper 26, as illustrated in FIG. 2. Press ram assembly I6 is actuated through drive 32 to move towards die assembly 14. The die assemblys movable die segments 20 are, at this point, in their open, blank-receiving position. With continued movement of press ram assembly 16, piston punch 30 will enter the neck of the preformed blank and the neck die portion will engage the blank. With this engagement, die stripper 26 will begin to lower to begin to close movable die segments 20 into their article or blank reforming position. At about this time, fingers :34 will strike clamp members 52 to force these members over bosses 56 of die holder 38. Shoulders 54 of clamp members 52 will then hold neck die assembly 28 in place. This is the configuration illustrated in FIG. 2. At the time that clamp members 52 engage bosses 56, the neck die portion, movable die segments and die stripper are locked together in their articlereforming position. The press ram will continue to move toward die assembly 14 to pressurize the hydraulic fluid within blank 36 by piston punch 30 displacing the fluid to produce a reformed article. After the completion of the article-reforming process, press ram assembly 16 is moved away from die assembly 14, thereby moving fingers 64 away from clamp members 52, allowing springs 58 to open the clamp members and release neck die assembly 28.

Thus, downward movement of press ram 22 and piston punch 30 acts to compress fluid within blank 36, which hydraulically forms blank 36 into the desired shape. Due to clamp members 52 and the angled engagement of the mated movable die segments within die body 24 (to be fully described subsequently), and because substantially all of the forming cavity is defined by movable die segments 20, the force of the compressed fluid acting against ram assembly 16 is relatively small. That is, the substantial force exerted by the compressed fluid in prior art apparatus on their press ram assemblies, by using upper and lower dies which are brought into contact along a peripheral line of largest diameter, is significantly reduced in the apparatus of this invention, since most of such force is transferred through the movable die segments to the die body and press bolster 12. Clamp members 52 augment this force relief by transferring load to the press bolster.

FIGS. 3 through 6 illustrate the apparatus shown in FIGS. 1 and 2, except for the holddown mechanism, in greater detail.

A transverse slot 72 of press ram assembly 16 receives a crossbar 74. This crossbar effectively floats in the transverse slot. The weight of the crossbar may, however, be carried by support springs (not shown) for load reduction purposes. Press ram assembly 16 and crossbar 74 are coupled to permit a limited amount of relative movement between the two. Adjustable limit stops 76 are mounted on a support structure 78 of hydraulic forming apparatus 10, shown in FIG. 1, for limiting travel of crossbar 74 away from die assembly 14. During movement of press ram 22, after a forming operation, crossbar 74 engages adjustable limit stops 76 such that, upon continuing upward movement of the press ram, the crossbar contacts a stripper slide 80 to exert force on a stripper sleeve 82 through pushrods 84 so that the reformed article is readily ejected from neck die assembly 28.

The die body 24, shown in a lower portion of FIG. 3, has a tapering die-receiving cavity 86 centrally disposed below the press ram assembly 16 for receipt of movable die segments 20 and a corresponding number of stationary die segments 88. The stationary die segments occupy the outer radial portion of the die receiving cavity and are supported by a shoulder 54 of die body 24. Each of the stationary die segments has an inter nal, inclined wall 90. Each inclined wall has a dovetailed groove 92 for proper positioning and tracking of the movable die segments in their movement between their preformed blank-receiving-reformed article discharge position and article or blank reforming position. For proper tracking and positioning, each die segment has a corresponding dovetail 94 for engagement with the grooves.

As shown in FIG. 5, four die segments 20 are disposed within die-receiving cavity 86. By means of the dovetail engagement of each movable die segment with its groove in the corresponding stationary die segment 88, each movable die segment is movable into a mating position within the diereceiving cavity to define the forming cavity of the apparatus. The die segments are spaced apart at 90 angles to one another, and each has abutting surfaces 96 which are inclined at 45 relative to the movable segment's centerline to allow abutting of the movable die segments in their reforming position.

When in a closed or reforming position, the die segments define an internal forming cavity 98, shown in FIG. 4, which communicates with the exterior of die body 24 through a bore 100. This opening can be of a smaller cross-sectional area than the greatest cross-sectional area of the reforming cavity so as to permit the reforming of articles into a variety of complex configurations.

As shown in FIG. 3, each die segment 20 has a radial recess or groove 102 proximate the bottom of the segment, the recesses of all the segments defining a circular engagement area around the inner walls of the segments. An annular, radially extending flange 104 of an axially movable segment support sleeve 106 engages and maintains die segments 20 in axial and radial alignment, and functions in combination with die opening and closing means to move the die segments to both a spaced-apart, preformed blank-receiving-reformed article discharge position and a closed reforming position. Segment support sleeve 106 is disposed within an insert 108 secured to die body 24. The lower end of the segment support sleeve is threaded to a cup 110 having an annular abutting surface 112 which contacts the insert 108 to limit travel of the segment support sleeve at its extended position. A compression spring 114 biases the cup and the sleeve toward the press ram assembly. By virtue of the spring force, aligning flange 104 of the segment support sleeve acts to return movable die segments 20 to a spaced-apart position after the press ram force is released following each reforming operation.

Die stripper 26 is axially disposed within bore 117 of segment support sleeve cup 110 and is capable of movement toward and away from the press ram assembly. The die stripper has a head 118 capping a body portion 119 which moves into and out of the volume defined by the inner surfaces of movable die segments 20. A compression spring 120 encircles a shaft portion 122 of the die stripper and engages the bottom of cup 110 and a shoulder 123 of the die stripper. Compression spring 120 biases the die stripper toward the press ram assembly to cause ejection of formed articles. A stop nut 124 is secured to the lower end of the die stripper shaft for limiting upward movement of the die stripper and the segment support sleeve.

The die segments are held in their spaced-apart position, as shown in FIG. 3, by compression spring 114 acting on the lower end of cup 110. The compression spring acts through the alignment flange 104 to effect upward movement of movable die segments 20 following each forming operation. When opened, die segments 20 are circumferentially spaced apart from each other as shown in FIG. 5.

The application of force, by press ram 22 through preformed blank 36 on die stripper head 118, overcomes the force of compression spring 120 and causes die stripper 26 to move downwardly until the underside of the head contacts the upper surface of alignment flange 104. Continuing downward movement of the die stripper thus imparts downward motion to movable die segments 20 through the alignment flange. The track of the die segments in their movement into the cavity will be downward and inward because of the angled disposition of the sidewalls of the cavity. The sleeve and die segments move in this downward direction until abutting surfaces of the die segments engage, at which point the internal walls of the die segments define forming cavity Q8 of the die, as shown in FIG. 4. At this i position the movable die segments are completely closed by surface 126 contacting surface 127 of the movable die segments. That is, the press ram assembly through neck die assembly 28 maintains movable die segments 20 in their forming position during the reforming of blank 36. In the closed position, a convex upper surface 128 of die stripper head 118 defines the bottom surface of the forming cavity.

Upon release of the force exerted on movable die segments 20 by the press ram, compression spring 114 of the segment support sleeve urges the die segments back to their spacedapart position. Similarly, spring 120, biasing the die stripper towards the pressram, carries the die stripper back to its original position as shown in FIG. 3.

Piston punch 30 and neck die assembly 28 of press ram as sembly 16 are in axial alignment with the longitudinal axis of symmetry of all the die segments 20. The piston punch is mounted in the ram by a piston punch holder 129 disposed in longitudinal bore 131) of the ram assembly. An intermediate portion of the piston punch holder has an annular flange 131 secured to a mounting plate 132 of the press ram assembly by a plurality of threaded bolts 133. Mounting plate 132 is secured to the end of the ram by bolts 134. A setscrew 135, as shown in H0. 4, is disposed in a threaded aperture 136 of piston punch holder 129 and engages, at an indentation 137, the piston punch. The setscrew serves to retain the piston punch in a bore 138 of the piston punch holder.

The piston punch is a tubular member having a center portion 139 of enlarged diameter. This piston punch holder receives the center portion of the piston punch in an enlarged bore 140. A shoulder 141 of the piston punch holder engages center portion 139 of the piston punch and transmits downward axial force of the press ram to the piston punch.

The piston punch has a radial aperture disposed at its upper end which communicates with a length of pressure tubing 142. The piston punch has an internal bore, suitable for passage of the hydraulic fluid used in pressure reforming blank 36, which is closed at the upper end of the piston punch by a plug 143. The bottom end of the piston punch has a port 144 by which the central bore of the piston punch communicates with the exterior. This end of the piston punch also has an extension 145 which is threaded to center portion 139 and which contains a fluid check valve 146 for preventing reverse flow of liquid through port 144. Alternately, where a check valve is omitted, this end of the piston punch is integrally constructed with the remainder of the piston punch.

The periphery of extension 145 adjacent port 144 includes a plurality of axially spaced, transverse slots 147 which communicate with an axial bore 148 eccentrically disposed within the piston punch. A metering screw 149 is disposed within the bore and can be adjusted for closing of one or more of the transverse slots of the bore.

As seen in FIGS. 1 and 4, a fluid pressure pump 150 is connected to the free end of the pressure tubing and supplies fluid under pressure to the internal bore of the piston punch. The pressure pump is secured to the press ram by a bracket 151 and is energized by press ram assembly 16, as described below.

Neck die assembly 28 has a bore 152 suitable for slidable engagement with the neck of blank 36. Neck die portion or annular ring 34 projects from the face of the neck die assembly and encircles the bore. The outer diameter of the annular neck die portion is slightly less than the diameter of opening or bore 11111 of the forming cavity 98 defined by the die segments. The neck die portion, thus, is capable of extending into the forming cavity bore when the neck die assembly is moved downwardly into contact with the die segments.

The neck die assembly is received in an enlarged portion of a bore in neck die holder 38 and secured thereto by bolts 153, as shown in FIG. 3. The remainder of the neck die holders bore is capable of slidably engaging the periphery of the tubular end of piston punch holder 129. Neck die holder 38 has a flange 154 projecting radially outward from the centerline or axis of the holder and is provided with a plurality of equally spaced holes 155 which receive a plurality of elongated bolts 156, shown in FIG. 4. The bolts engage threaded bores in the mounting plate and mount the neck die holder on the mounting plate. Compression springs 40 bias the neck die holder into engagement with the heads of the bolts. The neck die holder is axially movable toward the piston punch holder until its end face 157 proximates mounting plate 132 of the press ram as sembly.

Stripper sleeve 82 is disposed between the piston punch and the central bore defined by the neck die. It extends from adjacent the annular ring on the neck die into the bore and terminates in an end flange 158. A pair of pushrods is mounted in axially oriented grooves of the piston punch holder as shown in FIG. 3. The pushrods engage a movabld stripper slide extending into the bore of the piston punch holder. The stripper slide includes an axially projecting lug 159 at its upward end. A cutout 160 is provided for allowing free relative movement between the stripper slide and the piston punch.

ln instances where the deformation of the article requires more displacement offluid than the diameter and stroke of the piston punch affords, it is sometimes necessary to inject additional fluid into the article to obtain a full deformation. This might occur, for example, where the neck of the article to be formed has a small diameter in comparison with the main body of the part. Pressurized fluid can then be introduced into the body of the article from pressure pump 150 during the forming operation.

Pressure pump 150 has a cylindrical housing mounted on the press ram by bracket 151, and an axially movable, elongated piston 172, disposed in the housing. Piston 172 projects past the housing and has a center portion of enlarged diameter exteriorly to the housing. A sleeve 174 of the housing is provided for guiding the center portion of the piston during its axial movements within the housing. A pin 176 projects radially from the center portion through an elongated slot 177 in the sleeve and secures an annular ring 178 to the piston, the annular ring encircling the periphery of sleeve 174. A compression spring 180 is disposed between the housing and the annular ring and serves to bias the piston away from the housing. Travel of the piston is limited by the length of slot 177 and its engagement with pin 176. An end of the piston furthest removed from the housing projects past the sleeve and engages an axially adjustable setscrew 182 mounted in a block 184.

Adjustment of the setscrew 182 determines the travel of the piston during the downward motion of the ram. When piston 172 engages setscrew 182, the latter travels into the housing, thereby pressurizing fluid in the cylinder and forcing it out through a check valve 186, communicating the housing with the pressure tubing 142, port 144, and the interior of the article to be formed. The amount of liquid which the pump is required to eject is determined by the configuration of the article, the amount it is to be deformed, and the diameter and stroke of the piston punch. In each case, setscrew 182 is adjusted accordingly. A second check valve 188, shown in FIG. 4, connects the cylinder with a fluid source 1'98. If no additional fluid is required during the forming operation, setscrew 182 is removed or adjusted so that it does not contact the free end of the piston during any part of the motion of the ram.

In operation of the press, press ram 22 is retracted from die assembly 14, thereby enabling the springs 114, 120 to respectively move sleeve 106 and die stripper 26 into the first limiting position as shown in FIG. 3. This first limiting position corresponds to the preformed blank-receiving-reformed article discharge position. The article to be formed, which ordinarily is preformed, is placed on die stripper head 118 and filled with a fluid, such as water or oil.

The press ram, together with crossbar 74, mounting plate 132, piston punch 30 and neck die assembly 28, is moved toward die assembly 14 until an upper rim 162 of the preformed blank or article 36 to be formed is disposed in the annular space between the piston punch 30 and the bore in die portion of neck die assembly 28. The piston punch enters the hollow neck portion of the article to a point where the metering screw 149 cuts off escape of fluid from the interior of the article. The force of the press ram, during subsequent downward movement, is thereby transmitted through the fluid to die stripper 26, the article and die stripper thus being moved downwardly into the die assembly. The lower surface of head 118 of the die stripper then contacts annular flange 104 of sleeve 106, whereby continuing movement of the press ram is transmitted through the annular flange to the movable die segments 28 causing them to move downward and together towards a mating position around article 36, as shown in FIG. 4. This mating position corresponds to the article-reforming position and is the position which defines forming cavity 98. The movable die segments are maintained in this osition by engagement of neck die assembly 28 with the movable die segments.

During the initial downward movement of the press ram, axial force is imparted by the upper rim of the article to stripper sleeve 82 and through push rods 84 to stripper slide 80, causing the stripper slide to move upwardly within the bore of the piston punch holder.

The movement of piston punch 30 and neck die assembly 28, while moving the die stripper head towards annular flange 104, also causes the end face of annular ring 34 to engage the largest cross-sectional area of the article being formed. Springs 40 of the press ram exert a greater force than that exerted by spring 120 encircling the die stripper shaft, whereby the neck die and piston punch continue to move into the die body cavity. A degree of preforming can be accomplished by proper adjustment of the pressure of spring 120 resisting the downward movement of the die stripper.

Continued motion of the press ram brings end face 126 of the neck die assembly 28 adjacent annular ring 34 into contact with a face of movable die segments 20. The axial force exerted by compression spring 114 on cup 110, transmitted through the segment support sleeve 106 to the die segments 20, is now additionally transmitted to the springs 40 of the press ram. Press ram springs 40 are sized such that they exert sufficient force to overcome this additional force, thereby causing movable die segments to move along the dovetail grooves of the cavity walls and into mating relationship with each other.

Movement of the die segments 20 is also effected, as noted above, by the support segment sleeve 106 and its aligning flange 104. That is, as the die stripper continues in downward direction in response to the force of the press ram, force is transmitted by flange 104 to die segments 20 until the mating position is reached, after which no additional movement of either the die segments or the neck die is possible. The closed die segments, annular ring 34, and convex upper surface 128 thus define the forming cavity 98, the article to be formed being held in the forming cavity for the pressurization operation.

Downward motion of the press ram is continued to cause relative movement between the neck die and neck die holder 38 on the one hand, and between piston punch 30, piston punch holder 129 on the other hand. When the last transverse slot 147 of the piston punch moves past upper rim 162 of the article, flow communication between the interior of the article and the exterior is interrupted, except for a minute annular gap between the walls defining the neck of the article and the outside surface of the piston punch. The effects of such a gap can be disregarded if the forming operation is conducted at a relatively high speed, since under such conditions the fluid is trapped within the article. The movement of the piston punch serves to displace the liquid within the article, thereby subjecting the walls of the article to high pressure. The walls yield under the pressure and move outwardly until they contact the forming walls of the die segments, the upper surface of the die stripper head (convex surface 128), and annular ring 34, thereby assuming the shape of the forming cavity.

During the pressurization operation, axial forces are exerted upon both die stripper 26 and the neck die assembly 28. Forces exerted on the die stripper are transmitted to the die segments by aligning flange 104 such that the die segments are forced into contact with each other. The neck die and the neck die holder are maintained in the forming position, during the pressurization operation, by either the force exerted by press ram springs 40 or clamp members 52, as shown in FIG. 2, or both. Neck die assembly 28 and neck die holder 38 are constructed so that end face 157 of the neck die holder proximates the lower surface of the mounting plate of the press ram when the piston punch has reached its lowermost position, at which point the article has been fully formed.

Movable die segments 20 also are subjected to radial forces which urge them outwardly, resulting component axial forces in the direction of the press ram. These component forces are a function of the angular inclination of engagement between movable die segments 20 and stationary die segments 88. By decreasing the inclination of the engaging surfaces of the movable and stationary die segments relative to the axis of force of the press ram, the axial force of the pressurized fluid against the press ram can be significantly reduced. As a result, low-capacity press ram assemblies can be utilized in maintaining the dies in a closed position during the pressurization operation.

Upon completion of the forming operation, the press ram is moved away from the die assembly. During the return stroke, the above described steps occur in reverse order until the press ram reaches its original position and the die segments are in the spaced-apart position shown in FIG. 3. The neck die stripper is caused to eject the formed article by action of the crossbar 74, stripper slide and push rods 84 on the stripper sleeve 82. Another article is then placed on the die stripper head and the cycle can be repeated.

Check valve 146 provides for preventing formation of a vacuum within the formed article during the return stroke of the piston punch. Vacuum occurring within the formed part, during retraction of the piston punch, opens the valve and permits fluid to enter the interior of the article from the bore of the piston punch. As the piston punch passes upper rim 162 of the article, the release of vacuum in the article again closes the valve to prevent the unnecessary flow of liquid through port 144. 1

We claim:

1. An apparatus for pressure reforming of hollow blanks into reformed articles comprising:

a. a base including a die body;

b. at least two displaceable die segments disposed in the die body for movement between a spaced-apart, blankreceiving-reformed article discharge position and a blank-reforming position, the die segments in their blankrefon'ning position defining at least a portion of a forming cavity and a bore, the bore having a diameter less than the maximum diameter of the forming cavity and opening into the forming cavity, each of the die segments in its blank-reforming position being supported by the die body at an interface disposed at an acute angle to the longitudinal axis of the forming cavity, the angle being such that the force required to maintain the movable die segments in their forming position is less than the force generated by the pressure reforming of an article which tends to move the die segments apart;

c. a press ram assembly including a piston punch, the piston punch being operable to enter the bore to displace a fluid within a hollow blank in the forming cavity and thereby reform the blank into a reformed article, the press ram assembly having means to exert a force to maintain the die segments in their blank-reforming position during the displacement of fluid by the piston punch;

d. means for reciprocating the press ram assembly to and away from the die segments;

e. means for supporting the press ram assembly;

f. means for moving the die segments from their blankreforming position to their blank-receiving-reformed article discharge position;

g. a displaceable sleeve in the die body having an annular flange for engaging the die segments;

h. an annular recess in the die segments receiving the flange of the sleeve;

i. biasing means for urging the sleeve toward the press ram assembly and the die segments into their blank-receivingreformed article discharge position, the die segment moving means including the sleeve-biasing means;

j. a die stripper having a shaft received in the sleeve and a head, the head defining a portion of the forming cavity in the blank-reforming position and being engageable with the sleeve such that force exerted on the head from the press ram assembly is transmitted to the sleeve; and

llllv k. biasing means for urging the die stripper head away from the sleeve toward the press ram assembly.

2. The apparatus claimed in claim 1 wherein the die body defines a plurality of walls, corresponding to the number of die segments, which diverge toward the press rarn assembly, each wall and a corresponding die segment engaging each other through a dovetail slide and groove such that the die segments are held in contact with the walls during their movement.

3. The apparatus claimed in claim 1 wherein the press ram assembly includes:

a. a neck die assembly having an annular neck die which receives the piston punch, the neck die being disposed for movement into the bore when the die segments are in their reforming position to define a portion of the forming cavity, the neck die assembly having means to engage the die segments and exert the force required to maintain the die segments in their blank reforming position during displacement offluid by the piston punch; and

b. means for moving the piston punch into a hollow blank in the forming cavity after the neck die assembly engages the die segments.

4. The apparatus claimed in claim 3 additionally comprising means for removing formed articles from the neck die during movement of the press rarn assembly away from the die segments.

5. The apparatus claimed in claim 4 wherein the removing means comprises:

a. a crossbar disposed within a slot of the press ram assembly;

b. stop means for limiting travel of the crossbar in relation to the press ram assembly;

c. a stripper slide disposed within the press ram assembly and capable of axial movement therein;

d. a stripper sleeve disposed within the neck die assembly of the press ram; and

e. push rods disposed between the stripper slide and the stripper sleeve such that during motion of the press ram assembly away from the die segments the crossbar will contact the stop means to exert downward pressure through the stripper slide and push rods to the stripper sleeve, thereby effecting removal of the formed article from the neck die.

6. The apparatus claimed in claim 1 additionally comprising a fluid pressure pump mounted on the press ram assembly, the pump having an axially movable piston and a cylinder in flow communication with a bore of the piston punch which is capable of fluid communication with the interior of a hollow blank, the piston being engageable by the support means of the press ram assembly during at least a portion of the movement of the piston punch towards the die segments, whereby fluid is compressed during movement of the press ram assembly towards the die segments.

7. In a punch press for reforming hollow articles wherein a piston punch of a reciprocatable ram assembly is insertable into a preformed blank in a forming cavity to pressurize fluid within the blank to effect its forming, an improvement comprising:

a. a die body having at least two inclined walls diverging towards the ram assembly;

b. a die segment for each inclined wall, each die segment being slidably engaged with its corresponding inclined wall, the die segments being movable to both a mating position and a spaced-apart position, the die segments in their mating position defining a forming cavity and a bore opening into the forming cavity for passage of the piston punch, the forming cavity having a maximum diameter exceeding the diameter of the bore;

c. means for urging the die segments to their spacedapart position;

d. means including the ram assembly for moving the die segments into their mating position and for maintaining the die segments in their mating position during the pressurizing offluid in a blank;

e. a coordinating member defined by a sleeve having an annular flange, the die segments having a recess which receives the annular flange to provide engagement between die segments and the sleeve such that movement of the sleeve towards the ram assembly produces movement of the die segments toward their spaced-apart posi tion and movement of the sleeve away from the ram assembly produces movement of the die segments toward their mating position, the die segment urging means being operable to bias the sleeve towards the ram assembly;

f. a die stripper having a head and a shaft extending from the head and received in the sleeve, the die stripper being coupled with the sleeve such that the head is in a first position toward the ram assembly to receive a preformed blank when the die segments are in their spaced-apart position and in a second position relatively away from the ram assembly and the first position when the die segments are in their mating position, the die stripper head being adapted to receive a preformed blank and to transmit force from the ram assembly to the sleeve to move the die segments into their mating position, the die stripper head in its second position defining a portion of the forming cavity; and

g. biasing means to couple the die stripper to the sleeve such that the head is spaced from the sleeve in the heads first position and in engagement with the sleeve in the heads second position, whereby refonning forces on the head are transmitted through the sleeve to the die segments to aid in maintaining the die segments in their mating position.

8. The improvement claimed in claim 7 additionally comprising holddown means operable to engage the ram assembly and transmit reforming forces acting in the direction of the press ram assembly to the die body.

9. The improvement claimed in claim 8 wherein the holddown means includes:

a. at least two clamp members pivotally secured to the die body;

b. biasing means to urge the clamp members into an open position; and

c. an actuating finger for each clamp member mounted through biasing means to the press ram assembly such that the fingers engage the clamp members and force such clamp members into holddown engagement with the ram assembly when the die segments are in their mating position while the piston punch enters a preformed blank in the forming cavity.

10. The improvement claimed in claim 7 additionally comprising pressure pump means for pressurizing a preformed blank in the forming cavity through a bore in the piston punch.

ill. The improvement claimed in claim 10 wherein the pressure pump means includes:

a. a fluid pressure pump on the press ram assembly;

b. an axially movable piston disposed within a bore of the fluid pressure pump in pressure communication with the piston punchs bore; and

c. means to move the piston within the bore to pressurize fluid in the preformed blank at a predetermined time during the reforming thereof.

12. In an apparatus for pressure preforming articles from hollow, preformed blanks wherein a piston punch of a reciprocating press ram assembly pressurizes fluid within the blanks when the blanks are held within a forming cavity defined by the inner walls of die segments, an improvement comprising:

a. a die body having at least two walls at an acute angle to the line of movement of the press ram assembly, the walls converging in a direction away from the press ram assembly;

b. a die segment for each wall of the die body, the die segments being slidably engaged with the walls such that they are capable of converging movement together away from the press ram assembly into a mating position, the die segdisposed within the sleeve, the head defining a portion of the forming cavity when the die segments are in their mating position and extending toward the ram assembly from its forming cavity position when the die segments are in their open position;

e. biasing means coupling the die stripper to the sleeve such that the die stripper is capable of greater movement than the sleeve and the die stripper engages the sleeve when the die segments are in their mating position;

. means for biasing the sleeve and the die stripper toward the press ram assembly;

g. a neck die assembly of the press ram assembly, the neck die assembly having a neck die capable of disposition within the bore defined by the die segments, the neck die assembly being operable to engage the die segments in their mating position to maintain the die segments in the mating position during reforming of a blank; and

. the piston punch being capable of transmitting force from the press ram assemblythrough a preformed blank to the die stripper head so as to move the die segments into their mating position.

13. The die assembly claimed in claim 12 wherein the die segments are engaged with the inclined walls through dovetail slides and grooves.

14. An apparatus for pressure reforming of hollow blanks into reformed articles comprising:

a. a base including a die body;

b. at least two displaceable die segments disposed in the die body for movement between a spaced-apart, blankreceivingreformed article discharge position and a blank-reforming position, the die segments in their blankreforming position defining at least a portion of a forming cavity and a bore, the bore having a diameter less than the maximum diameter of the forming cavity and opening into the forming cavity, each of the die segments in its blank-reforming position being supported by the die body at an interface disposed at an acute angle to the longitu dinal axis of the forming cavity, the angle being such that the force required to maintain the movable die segments in their forming position is less than the force generated by the pressure reforming of an article which tends to move the die segments apart;

c. a press ram assembly including a piston punch, the piston punch being operable to enter the bore to displace a fluid within a hollow blank in the forming cavity and thereby reform the blank into a reformed article, the press ram assembly having means to exert a force to maintain the die segments in their blank-reforming position during the displacement of fluid by the piston punch;

d. means for reciprocating the press ram assembly to and away from the die segments;

e. means for supporting the press ram assembly;

f. means for moving the die segments from their blankreforming position to their blank-receivingreformed article discharge position;

g. die stripper means associated with the die segments for carrying a blank to be reformed into the forming cavity as the die segments move to their reforming position and for discharging a reformed article from the die segments; the die stripper means including i. a displaceable head axially aligned with the bore, the

head having a surface which defines a portion of the forming cavity, the head being disposed to carry blanks U and reformed articles; and n. biasing means urging the head towards the press ram assembly from within the movable die segments to eject reformed articles and to accept a blank to be reformed; and h. means coupling the die stripper to the movable die segments such that the die stripper head moves to its position toward the press ram assembly when the die segments move towards their blank-receiving-reformed article discharge position, the coupling means including:

i. a displaceable coupling member in the die body having an annular flange for engaging the die segments;

ii. an annular recess in the die segments receiving the flange of the coupling member; and

iii. biasing means for urging the coupling member toward the press ram assembly, thereby transmitting force to the die segments to move them into their blank-receiving-reformed article discharge position, the die segment moving means including the coupling member biasing means. 

1. An apparatus for pressure reforming of hollow blanks into reformed articles comprising: a. a base including a die body; b. at least two displaceable die segments disposed in the die body for movement between a spaced-apart, blank-receivingreformed article discharge position and a blank-reforming position, the die segments in their blank-reforming position defining at least a portion of a forming cavity and a bore, the bore having a diameter less than the maximum diameter of the forming cavity and opening into the forming cavity, each of the die segments in its blank-reforming position being supported by the die body at an interface disposed at an acute angle to the longitudinal axis of the forming cavity, the angle being such that the force required to maintain the movable die segments in their forming position is less than the force generated by the pressure reforming of an article which tends to move the die segments apart; c. a press ram assembly including a piston punch, the piston punch being operable to enter the bore to displace a fluid within a hollow blank in the forming cavity and thereby reform the blank into a reformed article, the press ram assembly having means to exert a force to maintain the die segments in their blank-reforming position during the displacement of fluid by the piston punch; d. means for reciprocating the press ram assembly to and away from the die segments; e. means for supporting the press ram assembly; f. means for moving the die segments from their blank-reforming position to their blank-receiving-reformed article discharge position; g. a displaceable sleeve in the die body having an annular flange for engaging the die segments; h. an annular recess in the die segments receiving the flange of the sleeve; i. biasing means for urging the sleeve toward the press ram assembly and the die segments into their blank-receivingreformed article discharge position, the die segment moving means including the sleeve-biasing means; j. a die stripper having a shaft received in the sleeve and a head, the head defining a portion of the forming cavity in the blank-reforming position and being engageable with the sleeve such that force exerted on the head from the press ram assembly is transmitted to the sleeve; and k. biasing means for urging the die stripper head away from the sleeve toward the press ram assembly.
 2. The apparatus claimed in claim 1 wherein the die body defines a plurality of walls, corresponding to the number of die segments, which diverge toward the press ram assembly, each wall and a corresponding die segment engaging each other through a dovetail slide and groove such that the die segments are held in contact with the walls during their movement.
 3. The apparatus claimed in claim 1 wherein the press ram assembly includes: a. a neck die assembly having an annular neck die which receives the piston punch, the neck die being disposed for movement into the bore when the die segments are in their reforming position to define a portion of the forming cavity, the neck die assembly having means to engage the die segments and exert the force required to maintain the die segments in their blank reforming position during displacement of fluid by the piston punch; and b. means for moving the piston punch into a hollow blank in the forming cavity after the neck die assembly engages the die segments.
 4. The apparatus claimed in claim 3 additionally comprising means for removing formed articles from the neck die during movement of the press ram assembly away from the die segments.
 5. The apparatus claimed in claim 4 wherein the removing means comprises: a. a crossbar disposed within a slot of the press ram assembly; b. stop means for limiting travel of the crossbar in relation to the press ram assembly; c. a stripper slide disposed within the press ram assembly and capable of axial movement therein; d. a stripper sleeve disposed within the neck die assembly of the press ram; and e. push rods disposed between the stripper slide and the stripper sleeve such that during motion of the press ram assembly away from the die segments the crossbar will contact the stop means to exert downward pressure through the stripper slide and push rods to the stripper sleeve, thereby effecting removal of the formed article from the neck die.
 6. The apparatus claimed in claim 1 additionally comprising a fluid pressure pump mounted on the press ram assembly, the pump having an axially movable piston and a cylinder in flow communication with a bore of the piston punch which is capable of fluid communication with the interior of a hollow blank, the piston being engageable by the support means of the press ram assembly during at least a portion of the movement of the piston punch towards the die segments, whereby fluid is compressed during movement of the press ram assembly towards the die segments.
 7. In a punch press for reforming hollow articles wherein a piston punch of a reciprocatable ram assembly is insertable into a preformed blank in a forming cavity to pressurize fluid within the blank to effect its forming, an improvement comprising: a. a die body having at least two inclined walls diverging towards the ram assembly; b. a die segment for each inclined wall, each die segment being slidably engaged with its corresponding inclined wall, the die segments being movable to both a mating position and a spaced-apart position, the die segments in their mating position defining a forming cavity and a bore opening into the forming cavity for passage of the piston punch, the forming cavity having a maximum diameter exceeding the diameter of the bore; c. means for urging the die segments to their spaced-apart position; d. means including the ram assembly for moving the die segments into their mating position and for maintaining the die segments in their mating position during the pressurizing of fluid in a blank; e. a coordinating member defined by a sleeve having an annular flange, the die segments having a recess which receives the annular flange to provide engagement between die segments and the sleeve such that movement of the sleeve towards the ram assembly produces movement of the die segments toward their spaced-apart position and movement of the sleeve away from the ram assembly produces movement of the die segments toward their mating position, the die segment urging means being operable to bias the sleeve towards the ram assembly; f. a die stripper haVing a head and a shaft extending from the head and received in the sleeve, the die stripper being coupled with the sleeve such that the head is in a first position toward the ram assembly to receive a preformed blank when the die segments are in their spaced-apart position and in a second position relatively away from the ram assembly and the first position when the die segments are in their mating position, the die stripper head being adapted to receive a preformed blank and to transmit force from the ram assembly to the sleeve to move the die segments into their mating position, the die stripper head in its second position defining a portion of the forming cavity; and g. biasing means to couple the die stripper to the sleeve such that the head is spaced from the sleeve in the head''s first position and in engagement with the sleeve in the head''s second position, whereby reforming forces on the head are transmitted through the sleeve to the die segments to aid in maintaining the die segments in their mating position.
 8. The improvement claimed in claim 7 additionally comprising holddown means operable to engage the ram assembly and transmit reforming forces acting in the direction of the press ram assembly to the die body.
 9. The improvement claimed in claim 8 wherein the holddown means includes: a. at least two clamp members pivotally secured to the die body; b. biasing means to urge the clamp members into an open position; and c. an actuating finger for each clamp member mounted through biasing means to the press ram assembly such that the fingers engage the clamp members and force such clamp members into holddown engagement with the ram assembly when the die segments are in their mating position while the piston punch enters a preformed blank in the forming cavity.
 10. The improvement claimed in claim 7 additionally comprising pressure pump means for pressurizing a preformed blank in the forming cavity through a bore in the piston punch.
 11. The improvement claimed in claim 10 wherein the pressure pump means includes: a. a fluid pressure pump on the press ram assembly; b. an axially movable piston disposed within a bore of the fluid pressure pump in pressure communication with the piston punch''s bore; and c. means to move the piston within the bore to pressurize fluid in the preformed blank at a predetermined time during the reforming thereof.
 12. In an apparatus for pressure preforming articles from hollow, preformed blanks wherein a piston punch of a reciprocating press ram assembly pressurizes fluid within the blanks when the blanks are held within a forming cavity defined by the inner walls of die segments, an improvement comprising: a. a die body having at least two walls at an acute angle to the line of movement of the press ram assembly, the walls converging in a direction away from the press ram assembly; b. a die segment for each wall of the die body, the die segments being slidably engaged with the walls such that they are capable of converging movement together away from the press ram assembly into a mating position, the die segments in their mating position define a forming cavity and a bore, the bore opening into the forming cavity for receiving the piston punch; c. a sleeve slidably disposed within the die body, the sleeve having an annular flange engaging the die segments in an annular recess thereof, whereby the die segments move along the walls in response to movement of the sleeve; d. a die stripper having a head and a shaft, the shaft being disposed within the sleeve, the head defining a portion of the forming cavity when the die segments are in their mating position and extending toward the ram assembly from its forming cavity position when the die segments are in their open position; e. biasing means coupling the die stripper to the sleeve such that the die stripper is capable of greater movement than the sleeve and the die stripper engages the sleeve when the die segments are in their mating position; f. means for biasing the sleeve and the die stripper toward the press ram assembly; g. a neck die assembly of the press ram assembly, the neck die assembly having a neck die capable of disposition within the bore defined by the die segments, the neck die assembly being operable to engage the die segments in their mating position to maintain the die segments in the mating position during reforming of a blank; and h. the piston punch being capable of transmitting force from the press ram assembly through a preformed blank to the die stripper head so as to move the die segments into their mating position.
 13. The die assembly claimed in claim 12 wherein the die segments are engaged with the inclined walls through dovetail slides and grooves.
 14. An apparatus for pressure reforming of hollow blanks into reformed articles comprising: a. a base including a die body; b. at least two displaceable die segments disposed in the die body for movement between a spaced-apart, blank-receiving-reformed article discharge position and a blank-reforming position, the die segments in their blank-reforming position defining at least a portion of a forming cavity and a bore, the bore having a diameter less than the maximum diameter of the forming cavity and opening into the forming cavity, each of the die segments in its blank-reforming position being supported by the die body at an interface disposed at an acute angle to the longitudinal axis of the forming cavity, the angle being such that the force required to maintain the movable die segments in their forming position is less than the force generated by the pressure reforming of an article which tends to move the die segments apart; c. a press ram assembly including a piston punch, the piston punch being operable to enter the bore to displace a fluid within a hollow blank in the forming cavity and thereby reform the blank into a reformed article, the press ram assembly having means to exert a force to maintain the die segments in their blank-reforming position during the displacement of fluid by the piston punch; d. means for reciprocating the press ram assembly to and away from the die segments; e. means for supporting the press ram assembly; f. means for moving the die segments from their blank-reforming position to their blank-receiving-reformed article discharge position; g. die stripper means associated with the die segments for carrying a blank to be reformed into the forming cavity as the die segments move to their reforming position and for discharging a reformed article from the die segments; the die stripper means including i. a displaceable head axially aligned with the bore, the head having a surface which defines a portion of the forming cavity, the head being disposed to carry blanks and reformed articles; and ii. biasing means urging the head towards the press ram assembly from within the movable die segments to eject reformed articles and to accept a blank to be reformed; and h. means coupling the die stripper to the movable die segments such that the die stripper head moves to its position toward the press ram assembly when the die segments move towards their blank-receiving-reformed article discharge position, the coupling means including: i. a displaceable coupling member in the die body having an annular flange for engaging the die segments; ii. an annular recess in the die segments receiving the flange of the coupling member; and iii. biasing means for urging the coupling member toward the press ram assembly, thereby transmitting force to the die segments to move them into their blank-receiving-reformed article discharge position, the die segment moving means including the coupling member biasing means. 